1. Field of the Invention
The present invention relates to a lid mounted on an open portion of a container body that contains a liquid such as a refreshing drink, and, more particularly, to a pull-tab for an easy-to-open container lid which is mounted on the lid.
2. Description of the Prior Art
Conventional easy-to-open containers of the above-described type are classified as being one of two types, a partial-open-type and a full-open-type. In such an easy-to-open container, a panel portion of the lid of the container is provided with a score defining a removable portion. To remove the removable portion from the panel portion of the lid and thereby open the easy-to-open container, the score is ruptured by the action of gripping and pulling upward a gripping portion of a pull-tab that is fixed to the lid by means of a rivet formed integrally therewith at a predetermined portion of the removable portion surrounded by the score, with the end of the pull-tab opposite the gripping portion acting as a support.
Recently, the pull-tabs have been made thinner with a view to promoting conservation of resources. To cope with this tendency, it was proposed in the specification of Japanese Patent Publication No. 12358/1970 that the rigidity of the pull-tab may be increased in order to prevent it from coming off the rivet by forming the portion surrounding a hole in the pull-tab through which the rivet is inserted into a bowl-like configuration. It was also disclosed in the specification of Japanese Utility Model Publication No. 421/1980 that a horizontally turned portion may be provided by turning the peripheral edge of the rivet insertion hole of the pull-tab upward so as to prevent the pull-tab from coming off the rivet. Further, Japanese Utility Model Laid-Open No. 98326/1983 proposes making the length of the distal end of the pull-tab where no turned reinforcing edge is provided to be smaller than the outer diameter of the recessed portion provided at the peripheral edge of the rivet insertion hole so as to provide sufficient strength to allow the container to be opened even if the thickness of the pull-tab is small.
The above-described proposals each have their own advantages, and are effective in providing a pull-tab having a thin wall. However, each of them also has its own problems: for example, the pull-tab disclosed in the specification of Japanese Patent Publication No. 12358/1970 has the disadvantage that the pull-tab readily comes off the rivet when the container is opened. Japanese Utility Model Publication No. 421/1980 involves the disadvantage that it requires a large amount of opening force even though it is effective in reducing the likelihood of the pull-tab coming off. The pull-tab disclosed in Japanese Utility Model Laid-Open No. 98326/1983 also suffers from the problem that the pull-tab readily comes off. Thus, there have been limitations in regard to the desire to reduce the thickness of a pull-tab.